Melt spinning apparatus



May 21, 1963 E. FLETCHER A 3,090,074

MELT SPINNING APPARATUS Filed Sept. 8, 1960 2 Sheets-Sheet 1 FIG. 1

y 1963 E. L. FLETCHER 3,090,074

MELT SPINNING APPARATUS Filed Sept. 8, 1960 2 Sheets-Sheet 2 Mal/I...-

"amy United States This invention relates to an improved process and apparatus for the melt spinning of organic filament-forming compositions to form filaments, yarns, ribbons and the like. More particularly, it relates to an improved process and apparatus for the spinning of synthetic filaments to reduce the incidence of mass per unit length variation in filaments so produced as well as to avoid streaks of an undesirable nature in textile products produced therefrom.

Conventional apparatus for the melt spinning of synthetic fibers consists of a melt grid upon which the polymer, in particulate form, is melted to form a melt pool, a metering pump, a filter pack containing a filtering medium and a spinneret containing one or more orifices through which the molten polymer issues in the form of filaments. Upon leaving the spinneret, the molten filament is then quenched or cooled to a solid form by means of a fluid medium which may be applied in the form of a cross-current flow of air, for example.

The flow of quenching fluid is normally controlled as regards velocity, temperature, volume and flow pattern in order to insure proper quenching without excessive lateral movement or fluctuation of the filaments while still in the molten state. In particular, problems of fiuc tuation increase with increased filament denier or the rate of throughput since higher quenching fluid flow rates are required to achieve proper quenching. As denier is increased the surface area per unit mass of filament is decreased and proper quenching becomes more difiicult. Similarly, increased throughput rate lowers effective residence time in the quenching zone with the same result. Quenching, in sum, has been the limiting factor in the development of processes including higher spinning speeds for synthetic fibers of higher denier per filament yarn counts such as 15 denier nylon monofilament and similar synthetic organic filaments.

It is an object of this invention to provide an improved process and apparatus for the spinning of synthetic fibers from molten organic filament-forming compositions at higher deniersand greater rates than heretofore. Other objects will become evident hereinafter.

The objects of the invention are accomplished, in general, by spinning the molten organic filament-forming composition through a spinneret under conditions such that the molten filament is cooled during its passage through the spinneret, thereby reducing the amount of quenching required exterior to the spinneret. The coo-ling is effected by providing a uniform flow of a cooling fluid such as air, inert gas, steam or heattransfer liquid against the central portion of the face of the spinneret. The device for obtaining a uniform flow permits the cooling fluid to contact the face of the spinneret or a recessed portion thereof or a heat-conducting body in contact therewith and conduct away the heated fluids without permitting them to come in contact with the extruded filament issuing from the spinneret.

The nature of the invention will be more readily understood through reference to the accompanying drawings, which are merely illustrative, and to the insuring description thereof.

FIGURE 1 is a fragmentary, sectional view through a spinneret embodying the cooling device of the invention;

atent FIG. 2 is a plan view taken on line IIII of FIG. 1, looking in the direction of the arrows;

FIG. 3 is a sectional view through a modified cooler assembly adapted to be readily attached to and removed from a spinneret; and

FIG. 4 is a sectional view through a spinneret plate adapted to receive the cooler assembly of FIG. 3.

In FIGS. 1 and 2, -1 designates a spinneret plate attached by any convenient means (not shown) to the supporting member 2, usually the filter pack of a spinning unit. The spinneret is provided with capillary openings 3, through which the filaments are extruded, and a cavity 11. Fixed in the cavity is a distribution plate 5, provided with a ring of orifices 4, and a cooling fluid inlet tube 8. Below the distribution plate 5 is a top plate 6 to which is fixed an exhaust tube 7. Tubes 7 and 8 are concentric. The inlet tube 8 is attached to a source of cooling fluid under pressure at 9 and the heated fluid leaves the exhaust tube at 10.

FIG. 3 represents a convenient form of the cooler unit which may be readily attached to a spinneret adapted to receive it. In the drawing, the casing represented by numeral 12 is provided with a circumferential slot 14 into which a locking spring 13- is inserted. The distribution plate '5' is provided \with a ring of orifices 4 and an inlet tube 8'. The exhaust tube 7 is connected to the plate 6. The top surface 16 of the casing 12 should be as flat as possible.

A spinneret plate adapted to receive the unit of FIG. 3 is shown in FIG. 4. It is essentially the same as the spinneret plate shown in FIG. 1. The body of the spinneret plate 1' is provided with capillaries 3 and a cavity 11'. Here the inner circumference of the cavity is provided with :a slot 18 adapted to engage the locking spring 13 and hold the unit securely in place, at the same time permitting of easy removal. The top inner surface 17 should also be flat in order to allow the surface 16 of the unit to contact it uniformly. An interacting system of keys and slots (not shown) of a known type may be employed if desired to insure secure interaction and a good heat exchange relationship through constant surface-tosurface contact.

-In all of the above modifications, a cooling fluid is pumped into the unit at a controlled rate and is permitted to exhaust into the atmosphere or to a receiver remote from the spun filaments. The cooling fluid impinges uniformly upon the top surface of the unit and carries heat away at a steady, controlled rate. The temperature of the spinneret plate is thus lowered within a controllable range and the filament or filaments issuing from it are cooled prior toleaving the spinning unit.

The following example will serve further to illustrate a specific embodiment of the invention, it being understood that the example is not to be construed as being limitative of the invention.

Example A spinneret of the type illustrated in FIG. 4 Was inserted in a sand holder used for spinning 15 denier monofilament textile yarn of nylon. A cooling unit similar to that shown in FIG. 3 was plugged into the cavity in the spinneret prior to starting the polymer flow. The cooling medium used was air at 70 F. The air flow through the cooler was varied over the range 0-0.318 cu. ft. per minute. The yarn was spun at a speed 40% greater than heretofore. Approximately to lbs. of yarn were drawn for each set of conditions. The streak ratings designated in the tabulated results are based on visual comparisons, on an arbitrary relative scale, of a section of fabric knit from the yarn being rated. The streaks in the knit fabric are due to short length denier non-uniformities which are in turn caused by the fluctuations or lateral movement of the filaments while they are in the quenching zone. The results may be listed as follows:

Denier Chimney Cooler uniformair flow, air flow, Streaks ity, 5:3 c.f.m. c.f.tu. rating sigma limits, percent 145 0. 000 2. 2 3. 2 145 0. 120 l. l 145 0. 184 1. 2 145 0.318 1. l 130 0.215 1.2 130 0. 318 1.2 6. 2

At a cooler airflow of 0.318 c.f.m. a. larger denier variation was apparently caused by freezing of the nylon polymer in the distribution chamber above the spinneret. The draw-twist performance of the yarn produced compared favorably with that of yarn produced at normal production rates.

As noted in the above example, the rate of cooling Lmust not be so high as to cause freezing of the polymer in any part of the spinning unit. In practice, the rate of cooling can becontrolled by varying the flow or the inlet temperature of the cooling fluid. Preheating of the cool ing fluid is achieved by the use of the concentric inlet and exhaust tubes. Varying the length of the exhaust tube will vary the amount of preheating the cooling fluid receives and aids in the control of the cooling rate. External means of preheating the cooling fluid may be employed.

In general, the cooling fluid must enter the cooler at the center of the spinneret in order to avoid uneven cooling. Similarly, in the unit of the type shown in FIG. 3, the contact between the surface of the cooler and that of the spinneret must be uniform for the same reason. Uneven or localized cooling will result in local viscosity variation which in turn will aifect the denier since the denier of individual filaments in the case of monofilamerit spinning shown in the example is determined by the metering effect of the spinneret orifices.

It will be readily apparent that the cooling medium may consist of an inert gas such as air or steam or a liquid such as water or other heat transfer liquid. However, for most purposes, air will be most convenient.

The shape of the cavity in the spinneret and the cool- 3 ing unit fitting therein need not be circular. Other shapes such as square, diamond, kidney and the like may be used to equal advantage in order to obtain uniform cooling.

Although the example is illustrative of nylon spinning, the invention is also applicable to the spinning of other organic filament-forming compositions.

It will be readily apparent that many variations are possible without departure from the scope of the invention which is accordingly intended to be limited only by the scope of the appended claims.

I claim:

. 1. In a melt-spinning apparatus, a spinneret plate having a cavity in the-outer face thereof, a top plate closing said cavity, a distribution plate in said cavity, and a pair of telescoped coolant conduits, the outer conduit being connected to .said top plate and communicating with said cavity between said plates, the inner conduit being connected to the distribution plate and communicating with said cavity on the opposite side thereof from said outer conduit.

2. Spinning apparatus for the melt spinning of an organic filament-forming composition, said apparatus comprising a spinneret plate having a cavity in the outer face thereof, a distribution plate in said cavity, and a pair of telescoped conduits, one .of said conduits passing through said .top plate and being connected to said distribution plate, the other conduit being connected to said top plate, said conduits communicating with the cavity through the respective plates for the delivery and exhaust of a fluid coolant, said cavity having a side wall, said spinneret plate being provided with a pattern of holes equally spaced from said side wall.

3. Spinning apparatus for the melt spinning of an organic filament-forming composition, said apparatus comprising a spinneret plate having a cavity in the outer face thereof, a distribution plate situated intermediate the inner face of said cavity and the outer edge thereof, said distribution plate being provided with a series of spaced orifices adjacent the outer circumference thereof, a top plate flush with the face of said spinneret, a first pipe passing through said top plate and connected to a circular orifice in the center of said distribution plate, and a second pipe connected to a circular orifice in the center of said top plate, the internal diameter of said second pipe being greater than the external diameter of said first pipe, said pipes being substantially concentric and adapted for the delivery and exhaust of a fluid coolant.

4. Spinning apparatus for the .melt spinning of an organic filament-forming composition, said apparatus comprising a spinneret plate having a cavity in the outer face thereof, a circumferential slot in the wall of said cavity, a cooling unit adapted to be inserted into said cavity and interact with said slot to be firmly retained in position, said unit comprising a flat-faced casing pro vided with circumferential spring groove containing a locking spring, said casing being provided with an internal cavity, a distribution plate situated intermediate the inner face of said internal cavity and the outer edge thereof, said distribution plate having a series of spaced orifices adjacent the outer circumference thereof, a top plate attached to the outer edge of said casing, a first pipe connected to a circular orifice in the center of said distribution plate, and a second pipe connected to a circular orifice in the center of said top plate, the internal diameter of said second pipe being greater than the external diameter of said first pipe, said pipes being substantially concentric and adapted for the delivery and exhaust of a fluid coolant.

References Cited in the file of this patent UNITED STATES PATENTS 902,850 Auchu NOV. 3, 1908 2,051,861 Jones Aug. 25, 1936 2,058,408 Butler ct al. Oct. 27, 1936 2,110,570 Eichengrun Mar. 8, 1938 2,294,266 Barnard Aug. 25, 1942 2,403,476 Barry et al. July 9, 1946 2,449,355 Wiley ct al. Sept. 14, 1948 2,634,553 Russell Apr. 14, 1953 2,706,365 Stalego Apr. 19, 1955 2,821,744 Spohn et al. Feb. 4, 1958 2,908,036 Russell Oct. 13, 1959 OTHER REFERENCES Screw Cooling in the Operation of Single Screw Extrusion Means, Sackett, SPE Journal, August 1957, p. 50 relied on. 

1. IN A MELT-SPINNING APPARATUS, A SPINNERET PLATE HAVING A CAVITY IN THE OUTER FACE THEREOF, A TOP PLATE CLOSING SAID CAVITY, A DISTRIBUTION PLATE IN SAID CAVITY, AND A PAIR OF TELESCOPED COOLANT CONDUITS, THE OTHER CONDUIT BEING CONNECTED TO SAID TOP PLATE AND COMMUNICATING WITH SAID CAVITY BETWEEN SAID PLATES, THE INNER CONDUIT BEING CON- 